Patent GB-1433339-A (GB)
Title: Cellular cushioning structure and method and apparatus for making the same
IPC: B32B7/03
Filed: 1973-04-25
Abstract: 1433339 Cellular laminated material and an apparatus and method for the manufacture thereof FMC CORP 25 April 1973 [19 June 1972] 19726/73 Heading B5N A cellular cushioning structure comprises a laminate of at least two superimposed flexible, fluid-impermeable plies 11, 13, the superimposed plies being hermetically sealed along selected continuous areas 33, 35 which define the peripheries of a plurality of individual pockets 43 within which is entrapped a fluid, e.g. a gas under pressure, the pressure of the entrapped fluid being such that the unsealed areas 43 of the plies which define the exposed walls of the pockets bow outwardly from the structure and are in a taut condition, at least one of the plies being a film formed of orientable thermoplastic polymeric material with its unsealed areas being in at least a partially shrunken condition from a molecularly oriented state. In a preferred embodiment, the structure comprises three plies, at least the two outer plies being films of the orientable thermoplastic polymer. Examples of suitable polymeric materials, which are preferably biaxially oriented are polyethylene, polypropylene, polyester, nylon and polyvinyl chloride. The other plies may be formed of regenerated cellulose, paper or fabric, which may be coated. The structure may be made by containing the fluid under pressure between the superimposed plies, the film having its molecules oriented along at least one of its axial directions, and the plies remaining superimposed are hermetically sealed along said areas to entrap the fluid in the pockets, and the unsealed areas of the film are heated to effect the shrinkage thereof. An apparatus for making the structure comprises means for continuously feeding the plies into superimposed relationship, means for sealing longitudinal edges of the successive portions of the superimposed plies, means for delivering the fluid under pressure in between the superimposed plies concomitantly with the sealing thereof, means for hermetically sealing the plies along the selected areas and means for heating the unsealed areas of the film. In the embodiment described, a pair of continuous films 11 and 13 are superimposed as they enter nip rollers 15 and advanced between nip rollers 17, one pair of the longitudinal edges of the films being sealed by co-operating heated rollers 19. Beyond the nip rollers 17, an elongated nozzle 21 extending transverse to direction of film travel delivers compressed air between the films through a plurality of nozzle jets 23. A pair of rollers 25 nips the unsealed longitudinal edges of the film as they approach the nozzle 21 and a pair of heated rollers 27 seals these edges immediately after they are advanced past the nozzle. A series of like electrically heated discs 29 fixed at spaced intervals to shaft 31 continuously bond the films at transversely spaced intervals 33, the films being sealed together at longitudinally spaced intervals 35 by electrically heated plates 37 projecting beyond the peripheries of rollers 39. The cellular product 41 is then continuously advanced through oven 47 within which the unseated, molecularly oriented film areas 45 are heated to such a degree only as to effect shrinkage thereof. When more than two plies are used a modified nozzle (Fig. 3, not shown) is used to deliver compressed air between each adjacent pair of layers.